Automatically deployable sonobuoy

ABSTRACT

A sonobuoy arranged to be dropped into the sea from an aircraft and automatically deployed into an operational configuration. The prelaunch configuration is generally cylindrical for ejection from a conventional airborne launching tube. After ejection, a rotochute at the upper end of the sonobuoy automatically opens to stabilize and retard descent. Upon impact with the water, the impact pressure on a movable bottom plate at the lower end of the sonobuoy forces a release rod upward along the longitudinal axis to release the rotochute. When the rotochute is jettisoned, an antenna retainer is pulled free by a lanyard attached to the rotochute thus permitting antenna and ground plane elements to erect. When the bottom plate moves inwardly a split retaining ring holding the plate is released and subsequent reduction of the impact pressure, permits a pair of leaf springs to force the bottom plate out. Cocomittantly, a hydrophone, lower electronics and compliant cable deploy from the bottom. The upper end of the sonobuoy is positively buoyant and remains at the water surface. That is, when the bottom plate falls away, the leaf springs move out of coextensive slots at the bottom of the sonobuoy housing and a hydrophone cup thereby permitting the hydrophone cup to drop off and the hydrophone and lower electronics to pay out. When the lower electronics is clear of the sonobuoy housing, an umbrellalike sea anchor opens to introduce vertical damping. A sea-activated battery slidable from the upper to lower ends of the buoy is retained in the floating portion of the sonobuoy and provides electrical power.

baited @tates Patent Kirby [54] AUTOMATICALLY DEPLOYABLE SONOBUOY Woodrow P. Kirby, l-licksville, Ohio [73] Assignee: The United States of America as represented by the Naval Air Systems Command [22] Filed: Mar. 18,1970

[2]] Appl.No.: 20,689

[72] inventor:

[52] US. Cl ..340/2, 9/8 [51] Int. Cl ..B63b 21/52 [58] Field oi Search. ..340/2; 9/8

' [56] References Cited UNITED STATES PATENTS 3,220,028 11/1965 Maes ..9/8

Primary Examiner-Richard A. Farley AttorneyR. S Sciascia and Henry Hansen [57] ABSTRACT A sonobuoy arranged to be dropped into the sea from an air- [4 Feb.29,i972

craft and automatically deployed into an operational configuration. The prelaunch configuration is generally cylindrical for ejection from a conventional airborne launching tube. After ejection, a rotochute at the upper end of the sonobuoy automatically opens to stabilize and retard descent. Upon impact with the water, the impact pressure on a movable bottom plate at the lower end of the sonobuoy forces a release rod upward along the longitudinal axis to release the rotochute. When the rotochute is jettisoned, an antenna retainer is pulled free by a lanyard attached to the rotochute thus permitting antenna and ground plane elements to erect. When the bottom plate moves inwardly a split retaining ring holding the plate is released and subsequent reduction of the impact pressure, permits a pair of leaf springs to force the bottom plate out. Cocomittantly, a hydrophone, lower electronics and compliant cable deploy from the bottom. The upper end of the sonobuoy is positively buoyant and remains at the water surface. That is, when the bottom plate falls away, the leaf springs move out of coextensive slots at the bottom of the sonobuoy housing and a hydrophone cup thereby permitting the hydrophone cup to drop ofi and the hydrophone and lower electronics to pay out. When the lower electronics is clear of the sonobuoy housing, an umbrellalike sea anchor opens to introduce vertical damping. A sea-activated battery slidable from the upper to lower ends of the buoy is retained in the floating portion of the sonobuoy and provides electrical power.

6 Claims, 5 Drawing Figures PAIENTEUFEBZS I972 3,646,505

sum 2 [1r 2 INVENTOR.

' WOODROW P. KIRBY 1 AUTOMATICALLY DEPLOYABLE SONOBUOY STATEMENT OF GOVERNMENT INTEREST BACKGROUND OF THE INVENTION The present invention relates generally to underwater acoustic signal detection systems and more particularly to improvements in air-dropped, automatically deployable sonobuoys of the type wherein impact with the water causes release and pay out of a hydrophone and suspension system from -a floating radio transmitter and power supply.

Efficient and reliable jettisoning or pay out of various parts of an air-dropped sonobuoy promptly after impact with the water are essential criteria for successful execution of ASW (antisubmarine warfare) operations. In its prelaunch condition, a sonobuoy is usually assembled into a cylindrical profile for. ejection from an airborne launching tube. Upon ejection over an ocean area of interest, the sonobuoy configuration commences a sequence of changes in order to carry out different functions. First, a rotochute or drogue is deployed as the sonobuoy enters the slip stream of the aircraft for stabilizing and retarding its free fall. Stabilization enables precise placement of the buoy in the water and retardation minimizes the tenninal velocity and water impact force. Upon entry into the water, various techniques are presently employed to further change the sonobuoy configuration into a sound detection and/or projection and radio receiving and/or transmitting system. Common to each technique are the general requirements that the stabilizing and retarding device must be jettisoned to enable unimpaired erection and operation of a radio antenna and an electroacoustic transducer must be paid out from a flotation unit to a desired listening or projecting depth. In general, such techniques have been found to be complex and expensive to manufacture, subject to premature operation during ordinary prelaunch handling or during launching, or prone to hang up of one or more elements after water entry. Occurrence of such undesirable events, of course, are logistically, economically and militarily unacceptable particularly as applied to airborne ASW operations.

SUMMARY OF THE INVENTION Accordingly, it is a general purpose of the present invention to provide a novel and improved release mechanism for an airdropped sonobuoy which is responsive to the impact pressure at water entry, will positively jettison stabilizing and retarding devices and ensure antenna and hydrophone deployment, and which is relatively immune to premature operation during handling, shipping, loading or launching. Another object of the invention is to provide a sonobuoy release mechanism which is relatively inexpensive to manufacture and assemble due to its simplicity of design and arrangement of parts. Other purposes and objects of the invention will become readily apparent from the detailed description of a preferred embodiment of the invention which will now be summarized as follows.

A release mechanism for an air-dropped sonobuoy which, in the prelaunch condition, defines generally an elongated 'cylindrical housing suitable for ejection from an airborne launching tube into the slip stream of the aircraft and having a stabilizing and retarding mechanism that is releasably secure at the upper end which deploys to an operable position when clear of the launching tube. The lower end of the housing includes an exposed bottom plate urged outwardly against a split retaining ring by respective one ends of a plurality of leaf springs pivotally connected intermediate their respective ends to a hydrophone retaining cup. The respective other ends register with slots in the lower end of the housing. A release rod extending along the length of the housing between the bottom plate and the upper end of the sonobuoy retains a hoop spring about the interface of the stabilizing and retarding mechanism and the housing. Slight upward movement of the plate on impact at water entry causes the rod to disengage the ends of the hoop spring and jettison the stabilizing and retarding mechanism. At the same time, the split retaining ring is disengaged allowing the bottom plate to drop out of the housing. The leaf springs are then free to pivot and disengage the hydrophone retaining cup from the housing permitting the hydrophone and suspension system to pay out from the sonobuoy housing which due to its positive buoyancy remains floating at the surface.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1a and lb represent upper and lower portions, respectively, in a longitudinal cutaway view of a preferred embodiment of an air-dropped sonobuoy having a release mechanism constructed according to the invention;

- FIG. 2 represents abottom view of the sonobuoy of FIG. lb;

FIG. 3 represents a slightly enlarged cross-sectional view of the lower end of the sonobuoy taken along the line 3-3 of FIG. 2; and

FIG. 4 is a pictorial representation in elevation of the sonobuoy in. a fully deployed condition in water.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. Is an lb, there is shown a sonobuoy according to the invention assembled in a prelaunch condition having a cylindrical housing 10. Upper and lower bulkheads l3 and 14 form a watertight compartment at the upper end of housing 10 for containing an upper electronics unit 11 mounted on a coaxial hollow column 12. Upper electronics unit 11 comprises a VHF transmitter whose output is connected through an insulated rod 18 telescoped inside column 12 to antenna and ground plane elements 16 (FIG. 4) adjacent to the upper surface of bulkhead 13. The antenna and ground plane elements 16 are constructed of spring steel pemtitting them to be spindled within a removable antenna retainer 17. Rod 18 is urged toward erection by spring means not shown.

A rotochute assembly 20 is releasably mounted on the upper end of housing 10 and includes four equiangularly spaced curved blades 21 (only three shown in FIG. la) hinged to a trunnion 22 which is rotatably mounted on a cap 23 for rotation about the longitudinal axis of housing 10. Cap 23 is affixed on the top of housing 10 by a hoop spring 24 within a circumferential groove formed at the interface of cap 23 and housing 10 by respective interrneshing U-shaped tangs 26 and 27. The ends of spring 24 have eyelets 28 which register with each other to receive-the hooklike end of a stiff release rod 29 extending down along the side of the housing 10. A lanyard 25 is connected between retainer 17 and cap 23 to cause the former to be pulled off of the spindled antenna and ground plane elements 16 when the latter is jettisoned.

To ensure positive buoyancy to housing 10, a sleeve 31 of foamed resin lines the housing 10 between bulkhead l4 and inwardly projecting stops 32 formed in housing 10.

Electrical power for the sonobuoy is derived from a battery package comprising a cylindrical holder 33 containing a silver-chloride cell activated by immersion in sea water. Holder 33 is slidable along the length of housing 10 and includes an annular flange 34 which is held against the outer surface of lower bulkhead 14 but engages stops 32 when holder 33 slides toward the bottom of housing 10 to improve the righting moment thereof. Housing 10 includes a plurality of openings 35 near the lower end for permitting sea water to flow freely upward past battery holder 33 to ensure a continuous supply of electrolyte.

Assembled below the battery package is a cable package comprising a single-conductor compliant cable 36 (FIG. 4) coiled in a canister 37 and electrically connects upper electronics unit 11 and the battery package at one end to a lower electronics unit 38 and hydrophone 41 at the other end. The electrical conductor of the cable is helically wound around a compliant core to permit housing 10, when floating, to rise and fall with a wave motion without changing the elevation of the cable at the other end. Fixed to the lower end ofrcanister 37 is a watertight lower electronics unit 38 and an umbrellalike collapsible sea anchor 39 peripherally attached about the canister 37 at the junction with lower electronics unit 38. Anchor 39 is constructed of fabric and stiffening rods hinged to permit folding against canister 37. After deployment, anchor 39 opens to dampen vertical motion of the unit 38 notwithstanding motion due to waves at the surface. The lower electronics unit 38 may contain signal processing and amplifying circuits, azimuth sensore, etc., as dictated by the particular sonobuoy functions required and electroacoustic transducers utilized.

Next below lower electronics unit 38 is an electroacoustic transducer 41 slidably contained in a cylindrical cup 42. Transducer 41 may include a plurality of piezoelectric elements, omnidirectionally and unidirectionally responsive, for sensing or projecting acoustic energy in water. In the illustrated embodiment, transducer 41 is a directional hydrophone. Transducer 41 is secured by three flexible straps to the bottom of unit 38 for acoustically isolating vibrations otherwise induced in the sonobuoy system while maintaining transducer 41 on the same azimuth as unit 38. Cup 42 is open at its upper end to permit it to fall off of transducer 41 when released from housing 10. The lower portion of cup 42 defines an enlarged hollow cylinder 43 whose periphery is contiguous with the inner surface of housing 10. Cylinder 43 terminates in an annular flanged portion 45 which abuts the lower edge of housing I and limits the upward position of cup 42.

Coaxially extending downward from the bottom of cup 42 is a cylindrical stud 44 terminating in an annular sawtoothlike groove 56. The upper face of groove 46 is normal to the cylindrical axis and the lower face forms a truncated cone having its smallest diameter at the upper face. As best seen in FIGS. 2 and 3, an annular bottom plate 47 fits loosely on stud 44 and urges the inwardly extending ends of a pair of fingerlike leaf springs upwardly. Springs 48 are pivoted intermediate their ends to diametrically opposite sides of cylinder 43, the pivotal axes being in parallel and in a plane normal to the length of housing 10. The other ends of springs 48 extend through openings 51 in cylinder 43 to abut the lower edges of opening 52 in housing 10. Bottom plate 47 is prevented from moving downward with the force of springs 48 by a split retaining ring .53 whose ends are normally urged open to an inside diameter greater than the diameter at the lower end of groove 46. The confronting ends of split ring 53, however, are compressed together until ring 53 is positively seated in groove 46. Ring 53 is held seated by its insertion in an annular recess 54 about the bottom edge of the opening in bottom plate 47.

Referring again to release rod 29, it slidably extends through bulkheads 13 and 14, liner 31 and cylinder 43 with its lower end abutting the upper surface of bottom plate 47.

OPERATION The modus operandi of the above-described sonobuoy and release mechanism should be apparent and will now be sum- :marized as follows. The sonobuoy in its generally cylindrical configuration with rotochute blades 21 retracted along the sides is launched rotochute-first from an appropriate aircraft dispenser. As the sonobuoy enters the slipstream of the aircraft, the rotochute blades open and the drag of the slipstream forces the blades to rotate. Consequently, with the blades rotating, the housing swings downward and the sonobuoy autorotates to a point almost directly below the starting point of autorotation. This allows precise placement of the sonobuoy over a water area of interest. Impact with the water forces bottom plate 47 upward driving release rod 29 out of eyelets 28 of hoop spring 24. The entire sonobuoy submerges a few feet under the surface of the water due to its original inertia and, as blades 21 strike the water, rotochute assembly separates from housing 10 pulling the antenna retainer 17 free of elements I6. Antenna and ground plane elements 16 unwind and rod 18 erects while the sonobuoy is still under water. Due to the positive buoyancy of the housing 10, it rises to float on the surface with the antenna assembly above the surface.

At the same time when bottom plate 47 is pushed upward, retainer ring 53 extrudes from annular recess 54 and springs open to drop off of stud 44. As the impact pressure disappears, spring 48 forces plate 47 down and ofi' of stud 44; the gravitational force on cup 42 pivots spring 48 out of openings 52, and the cup 42 is permitted to drop out. Hydrophone 41, and lower electronic unit 38 are now free to drop with cable 36 paying out from canister 37. Battery 33 also slides to the bottom of the housing 10 until flange 34 engages stops 32. Openings 35 in the lower end of the housing 10 adjacent to battery holder 33 insure continuous flushing of sea water in the battery cell. The final operating condition of the sonobuoy system in the water is shown in FIG. 4.

Some of the many advantages of the present invention should now be apparent. For example, an improved sonobuoy system has been provided which affords an efficient and reliable deployment technique that can be easily manufactured and assembled with relatively few parts. The system is particularly suitable for handling without fear of premature actuation of the deployment release mechanism. The novel release mechanism is readily adaptable to many types of buoys and stores requiring rapid and sure deployment of components and materials contained therewithin.

It will be understood, of course, that various changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. In a sonobuoy having an elongated positively buoyant housing, a rotochute mounted on the upper end of the housing, and an electroacoustic transducer and suspension system therefor deployable from the lower end of the housing; a release mechanism, comprising:

a first member slidably received in the lower end of the housing for retaining the transducer and suspension system therein and including a downwardly projecting stud;

a second member slidably mounted on said stud;

retaining means operatively connected between said stud and said second member for preventing downward travel of said second member on said stud; and

force-exerting means pivotally connected to said first member for simultaneously urging said second member downward against said retaining means and said first member upward against the transducer and suspension system in the housing;

whereby impact pressure at water entry of the sonobuoy sequentially releases said retaining means, first and second members and the transducer and suspension system from the housing.

2. Apparatus according to claim 1 wherein:

said stud includes an annular sawtooth groove at the distal end thereof;

said retaining means includes a split ring normally urged open to slide over said stud;

said second member includes an annular recess for receiving said retaining means when the ends of said split ring are compressed in said groove; and

said force-exerting means includes one end urged upwardly by said second member and the other end urged upwardly by the housing.

3. Apparatus according to claim 2 further comprising:

hoop spring means positioned in an annular groove formed by intermeshing edges of the rotochute and housing and having coaligned eyelets at the ends thereof; and

rod means slidable along the length of the housing having an upper end turned downward and received in said eyelets and a lower end abutting the upper side of said second member;

whereby upward movement of said second member disengages the upper end of said rod means from said eyelets to jettison the rotochute from the housing.

4. A sonobuoy system comprising:

an elongated positively buoyant housing;

a rotochute mounted on the upper end of said housing;

an electroacoustic transducer and suspension system in said housing deployable from the lower end thereof; and

a release mechanism operatively connected to the lower end of said housing for releasing said transducer and suspension system in response to impact pressure at water entry of the sonobuoy system having a first member slidably received in the lower end of said housing for retaining the transducer and suspension system therein and including a downwardly projecting stud, a second member slidably mounted on said stud, retaining means operatively connected between said stud and said second member for preventing downward travel of said second member on said stud and force-exerting means pivotally connected to said first member for simultaneously urging said second member downwardly against said retaining means and said first member upward against said transducer and suspension system in said housing.

5. Apparatus according to claim 4 wherein said release mechanism further comprises:

said stud including an annular sawtooth groove at the distal end thereof;

said retaining means including a split ring normally urged open to slide over said stud;

said second member including an annular recess for receiving said retaining means when the ends of said split ring are pressed in said groove; and

said force-exerting means including one end urged upwardly by said second member and the other end urged upwardly by said housing.

6. Apparatus according to claim 4 further comprising:

hoop spring means positioned in an annular groove formed by intermeshing edges of said rotochute and said housing and having coaligned eyelets at the ends thereof; and

rod means slidable along the length of the housing having an upper end turned downward and received in said eyelets and a lower end abutting the upper side of said second member;

whereby upward movement of said second member disengages the upper end of said rod means from said eyelets to jettison said rotochute from said housing.

Patent No. 3,646,505

Dated February 29, 1972 Inventor(s) Woodrow Kirby It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the front page, data element identifier [73] the Assignee "The United States of America as represented by the Naval Air Systems Command" should read The United States of America Signed end sealed this 17th day of April 1973.

(SEAL) 'Attest:

EDWARD M.PLETCHER,JR. ROBERT (jOTTSCHALK Attesting Officer COIIHIIlSSlOIlBI of Patents F ORM PO-105O (10-69) USCOMM'DC 60376-P69 fi U.S, GOVERNMENT PRINTING OFFICE: I969 O-36-334 UNETED STATES FATE @FFECE errmm'm a Patent No. 3,646,505 Dated February 299 1972 Inventor(s) Woodrow P. Kirby It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the front page, data element identifier [73] the Assignee "The United States of America as represented by the Naval Air Systems Command" should read The United States of America Signed and sealed this 17th day of April 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT QOTTSCHALK Attesting Officer Commissioner of Patents ORM PO-105O (10-69) USCOMM-DC 60375-P69 Q U.S, GOVERNMENT PRINTING OFFICE: 1959 O36-334 

1. In a sonobuoy having an elongated positively buoyant housing, a rotochute mounted on the upper end of the housing, and an electroacoustic transducer and suspension system therefor deployable from the lower end of the housing; a release mechanism, comprising: a first member slidably received in the lower end of the housing for retaining the transducer and suspension system therein and including a downwardly projecting stud; a second member slidably mounted on said stud; retaining means operatively connected between said stud and said second member for preventing downward travel of said second member on said stud; and force-exerting means pivotally connected to said first member for simultaneously urging said second member downward against said retaining means and said first member upward against the transducer and suspension system in the housing; whereby impact pressure at water entry of the sonobuoy sequentially releases said retaining means, first and second members and the transducer and suspension system from the housing.
 2. Apparatus according to claim 1 wherein: said stud includes an annular sawtooth groove at the distal end thereof; said retaining means includes a split ring normally urged open to slide over said stud; said second member includes an annular recess for receiving said retaining means when the ends of said split ring are compressed in said groove; and said force-exerting means includes one end urged upwardly by said second member and the other end urged upwardly by the housing.
 3. Apparatus according to claim 2 further comprising: hoop spring means positioned in an annular groove formed by intermeshing edges of the rotochute and housing and having coaligned eyelets at the ends thereof; and rod means slidable along the length of the housing having an upper end turned downward and received in said eyelets and a lower end abutting the upper side of said second member; whereby upward movement of said second member disengages the upper end of said rod means from said eyelets to jettison the rotochute from the housing.
 4. A sonobuoy system comprising: an elongated positively buoyant housing; a rotochute mounted on the upper end of said housing; an electroacoustic transducer and suspension system in said housing deployable from the lower end thereof; and a release mechanism operatively connected to the lower end of said housing for releasing said transducer and suspension system in response to impact pressure at water entry of the sonobuoy system having a first member slidably received in the lower end of said housing for retaining the transducer and suspension system therein and including a downwardly projecting stud, a second member slidably mounted on said stud, retaining means operatively connected between said stud and said second member for preventing downward travel of said second member on said stud and force-exerting means pivotally connected to said first member for simultaneously urging said second member downwardly against said retaining means and said first member upward against said transducer and suspension system in said housing.
 5. Apparatus according to claim 4 wherein said release mechanism further comprises: said stud including an annular sawtooth groove at the distal end thereof; said retaining means including a split ring normally urged open to slide over said stud; said second member including an annular recess for receiving said retaining means when the ends of said split ring are pressed in said groove; and said force-exerting means including one end urged upwardly by said second member and the other end urged upwardly by said housing.
 6. Apparatus according to claim 4 further comprising: hoOp spring means positioned in an annular groove formed by intermeshing edges of said rotochute and said housing and having coaligned eyelets at the ends thereof; and rod means slidable along the length of the housing having an upper end turned downward and received in said eyelets and a lower end abutting the upper side of said second member; whereby upward movement of said second member disengages the upper end of said rod means from said eyelets to jettison said rotochute from said housing. 